BEAM TRANSFORMER

摘要

A beam transformer (30) changes the aspect ratio of the transverse spatial intensity profile I(x,y) of a light beam, the beam transformer comprising first and second rotationally symmetrical curved reflecting surfaces (14, 18) so arranged that the beam is reflected from the first curved surface (14) and subsequently by the second curved surface (18), the first reflecting surface (14) being tilted, with respect to the local propagation direction z of the beam (12), substantially about the local transverse x axis of the beam, and the second reflecting surface (18) being tilted, with respect to the local propagation direction z of the beam (16), substantially about the orthogonal local transverse y axis of the beam (16). The beam transformer can be used to change a laser beam from one with a highly asymmetric transverse intensity distribution (eg a highly elliptical beam profile (10; 60)) into one with a substantially axially-symmetric transverse intensity distribution (eg a circular beam profile (22)) or vice versa. One important example of such an application is a solid-state laser or semiconductor laser with a highly asymmetric gain medium. The beam transformer may be used within a laser resonator or external to the laser.